User admin API returns integers instead of booleans on SQLite, or the documentation is incorrect

[squahtx]

Similar to #13505. Originally reported by @jplatte in https://github.com/matrix-org/synapse/pull/13509#issuecomment-1212916888:

Description

The first example on https://matrix-org.github.io/synapse/develop/admin_api/user_admin_api.html shows this:

    "is_guest": 0,
    "admin": 0,
    "deactivated": 0,
    "shadow_banned": 0,

but some of these fields are mentioned as being bool further down.